Meeting Abstract

P3.17  Monday, Jan. 6 15:30  When Fish School and When They Don’t: Test of a Simple Radial Network Model LONG, JH; WASSERMANN, S*; SICILIANO, AM; PORTER, ME; Vassar College; Vassar College; Duke University; Florida Atlantic University sowassermann@vassar.edu

Coordinated group behavior such as flocking and schooling may help individuals evade predators, find food, and locate mates. In many situations groups transition between ordered and unordered structure. One way to track group structure is to measure the amount of coordination and correlation between individuals. In small groups, in particular, it’s not always clear when an individual is operating independently or in response to cues from other members of the group. Our goal was to examine swimming behavior as a function of the size of the group and the behavior of a key individual in a schooling elasmobranch, the cownose ray, Rhinoptera bonasus. We measured the kinematics of individuals in groups of one, two, and five individuals before and after one individual was startled. Our hypothesis was that individuals would respond to the startled individual as a function of their distance from and bearing to that individual, as if in a simple radial network with a single, central node. From overhead videos of animals swimming in a 16-foot diameter tank, we measured group responses such as scatter, alignment of velocity vectors, and variance of speed; for individuals, we calculated distance from and bearing to the startled individual. Preliminary results show that (1) some individuals respond to the change in behavior of a startled individual, (2) group structure gains order in response to a single individual being startled, and (3) the magnitude of an individual’s response depends, in part, on its distance from and bearing to the startled individual. This work was supported by NSF IOS-0922605.